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DIY Hot Tub Solar Heating Answered

Hi. I have a solar tub heating system 3/4s complete. It's based on a 100W PV panel to drive a pump, charge the battery and supply the electronics. A 16.5 sq ft solar water collector to heat the water. The heart of the system is a (made in China) DST1020 water temperature controller. My first thoughts are to open the flow of hot water to the tub at around 25degC, and cut it of at around 34degC. Problem - this controller has a reputation as a great little device, but it's a b**ch to program, the various instructions online just don't work. All I want it to do is close the heating dry relay contact at 25C and open at 34C. Easy? No. Has anyone got experience of this controller?

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Downunder35m
Downunder35m

5 weeks ago

LOL

I had similar issues with my freezer.
I admit these controllers are quite fance, same for the STS1000 series, but for just a temp control they are totally overrated if you ask me.
Biggest problem with most is that the contacts are designed for fridge applications.
Means if there is no normal relay contact with NC AND NO things get complicated.
So, let me fill you in on a little secret ;)
Check the usual online stores and do a sear for "digital temperature controller", sort by cheapest price.
You will some small, white boxes with a few wires, simple LED display and two or three buttons, usually just two - for about 10 bucks.
On these dirt simple temp controlers you can set the min and max temps as you like.
Means you can reverse the switching functions by simply setting a higher low temp and a lower high temp ;)
No programming required either.
And the relay switches ON when activated.
A bit confusing if you set the temps the first time but once you got used to thinking the other way around these cheap things will do exactly what you want.
With a sensitivity of 0.1°C.
Only downside is that they do just that, so no fance blocking functions for power loss or timers to set to prevent starting too quickly in succession.
Temp is reched, relay goes on, temp is gone, relay goes off, nothing more, nothing less ;)